The research work, broadly conceived, is concerned with changes in human abilities over time. Presumably both maturation and experience are involved since the subjects are college age or younger. One set of projects involves following undergraduate students into graduate and professional schools to determine the pattern of validities of undergraduate grades, year by year, and of graduate and professional school admission test results. The hypothesis is that a continuing simplex matrix of intercorrelations will be found, indicating the development of highly specialized abilities. Another project investigates the effects of preparatory school attendance on later undergraduate performance. A third project investigates the changes in abilities that occur during the latter half of the public school period. These last studies use multivariate statistics in the crossed-lag panel correlation paradigm.